1. Field of the Invention
This invention relates to a formatting apparatus which formats a recording medium such as a disk. Primarily, this invention relates to a flexible disk apparatus and a flexible disk format used for the flexible disk apparatus. Particularly, this invention relates to a formatting (initialization) method for the flexible disk apparatus.
Although a flexible disk is generally called a floppy disk or a diskette, this specification, uses the terms "flexible disk", "Flexible Disk Cartridge (FDC)", which is an official term standardized by JIS (Japanese Industrial Standard) and ISO (International Organization for Standardization)/IEC (International Electrotechnical Commission), or simply "disk".
2. Description of the Related Art
A flexible disk apparatus according to the related art is illustrated in FIG. 33.
In FIG. 33, a flexible disk 34 and a disk cartridge 35 are set in a flexible disk drive (FDD) 91. The flexible disk 34 is rotated by a spindle motor 33. A head 36 formats the flexible disk 34 and accesses data from the flexible disk 34. The head 36 is positioned by a positioning step motor 32. The head 36 writes data on the flexible disk 34 in accordance with a write command from a write amplifier 30 and reads data from the flexible disk 34 in accordance with a read command from a read amplifier 31.
In FIG. 33, a controlling circuit 90 controls the FDD 91. The controlling circuit 90 includes a controller 80a which controls an operation of each unit in the FDD 91. The controller 80a formats the flexible disk 34 based on format information received from a computer 21. The controller 80a receives a track position and data from the computer 21 and controls the FDD 91 to write the data on the flexible disk 34. The controller 80a also receives the track position from the computer 21, reads data at the track position, and sends the data to the computer. The controller 80a performs write signal modulation, read signal modulation, switching of the head for read/write, transmitting a positioning pulse to the positioning step motor 32, and generating an ON/OFF signal to the spindle motor to format the flexible disk and read/write the data.
An index pulse is outputted from the spindle motor 33 to the controller 80a. The controller 80a receives the index pulse and formats the flexible disk 34.
In a flexible disk apparatus according to the related art, a formatting (initialization) operation, which provides a constant number of recording sectors in one disk rotation, is performed for each track. Normally, a sensor which generates a pulse at a specific angle position of the disk is provided. An index pulse generated by the sensor triggers formatting of each track. After a necessary number of sectors are provided by formatting, a gap code (track gap G4) is written until an index pulse after one disk rotation is detected. Due to this gap code, even if the disk rotates slower or faster than an allowable rotation speed range, a space is not generated in the one disk rotation and a first sector format is not damaged by being written over when a last sector is formatted.
A track position signal is often written magnetically on a large capacity flexible disk or a hard disk as a servo track during production in order to ensure track position accuracy for high density reading/writing. The servo signal is sometimes recorded in a space between sectors on a data recording surface. In that case, the sectors are also formatted based on the servo signal, i.e., a sector servo signal.
However, servo information used to position a track and a sector is not used to position a head for some recording mediums such as a normal capacity flexible disk. Reading from or writing to a recording medium such as a normal capacity flexible disk can be performed by predetermining the size and positions of recording sectors by formatting (initialization). The disk is formatted by a flexible disk apparatus for read/write before the disk is used. Alternatively, the disk is formatted during production and is sold in formatted form.
A flexible disk format used commonly is standardized by JIS, ISO, etc., for example, as follows:
a format of a double-sided, double density flexible disk with a diameter of 200 mm (8 inch) (1.6 MB):JIS X 6202, ISO7065-2, PA1 a format B of a double-sided, high density flexible disk with a diameter of 130 mm (5.25 inch) (1.6 MB):JIS X 6213, ISO8630-3, PA1 a format B of a flexible, high density disk with a diameter of 90 mm (3.5 inch) (2 MB):JIS X 6225, ISO/IEC9529-2, and PA1 a format of a high density medium with a diameter of 90 mm (3.5 inch) (4 MB):JIS X 6226, ISO/IEC10994. PA1 the index gap G1: a constant angle position on a disk or a spindle motor is detected by a sensor and an index pulse is generated for every disk rotation. In order to absorb instability of the angle position due to jitter (instability of a time position) of the index pulse, a gap signal of 146 bytes according to a standard, a code "4E" in this example, is written continuously as the index gap G1 just after formatting of a track is started in response to the index pulse. When the track formatting is completed by detecting a next index pulse after one disk rotation, even if the next index pulse is delayed, only part of the index gap G1 is deleted. Hence, an ID field of the sector identifier (ID) in the first sector is not damaged.
With reference to FIG. 34, the format B of the high density flexible disk with a diameter of 90 mm (90 mm FDC) with a pre-formatting nominal capacity of 2.0 MB is discussed as an example.
The high density flexible disk with a diameter of 90 mm for 2 MB (90 mm 2 MB FDC) has 80 tracks respectively on each of two surfaces. Each track has 18 sectors, each having a data recording capacity of 512 bytes. Formats for the double-sided, double density flexible disk with a diameter of 200 mm (200 mm FDC) and the double-sided, double density flexible disk with a diameter of 130 mm (130 mm FDC) are the same as the format of the 90 mm 2 MB FDC except for a number of sectors in a track, which is 16 for the 200 mm FDC and the 130 mm FDC. A format for the high density flexible disk with a diameter of 90 mm for 4 MB (90 mm 4 MB FDC) is almost the same as the format for the 90 mm 2 MB FDC except for the number of sectors in a track, which is 32 for the 90 mm 4 MB FDC, and the length of a sector identifier gap (41 bytes), which is longer than that needed for the 90 mm 2 MB FDC.
As shown in FIG. 34, formatting of each track is triggered by an index pulse. After formatting is triggered, an index gap G1, a sector identifier (ID), an ID gap G2, a data block and a data block gap G3 in a first sector, a sector identifier (ID), an ID gap G2, a data block and a data block gap G3 in a second sector, . . . , a sector identifier (ID), an ID gap G2, a data block, and a data block gap G3 in a last sector are written on the disk. Then, the track gap G4 is written until an index pulse after one disk rotation is detected.
When a track formatting is completed, formatting of a track with a same track number on another recording surface or a track in a next cylinder begins. When all tracks (all cylinders) on the disk are formatted, formatting is complete.
When data is written on the formatted disk, or the data stored on the disk is updated, a sector identifier (ID) indicating an address is read, and only a data block in an addressed sector is updated.
Each of the gaps functions as follows;
Some kind of a controller LSI (Large-Scaled Integrated Circuit) skips to read recorded content for a constant time after an index pulse of the apparatus is generated. Therefore, the index gap G1 of this length is also necessary to absorb errors (in a position at which the index pulse is generated) caused by a difference in apparatuses.
The ID gap G2 and the data block gap G3: when data is written or updated on a formatted disk, a sector identifier (ID) of a sector is read. When the sector having an address to which the data should be written is detected based on the sector identifier (ID), the magnetic head is switched to a write mode in a period between the sector identifier (ID) and the data block, and the data is written only in a field of the data block. The ID gap G2 is provided for the switching period between the sector identifier (ID) and the data block.
Additionally, erasing bands are provided on both sides of the data field of the data block so that old data is removed.
A magnetic head according to a tunnel erasing method is illustrated in FIG. 37.
In FIG. 37, a rotation line speed .nu. of a track, a minimum line speed .nu..sub.min and a maximum line speed .nu..sub.max are shown.
In the magnetic head according to the tunnel erasing method, an erasing (E) gap is behind a read/write (R/W) gap by a constant distance d. Therefore, when data is written, an erasing current which is transmitted to the E gap is raised after a constant time after a write current transmitted to the R/W gap is raised so that sufficient erasing bands are provided on both sides of the data field from starting and the ID field of the sector is not damaged. If the erasing current is transmitted to the E gap at the same time data update begins, the E gap might be in the ID field and contents of the ID field might be damaged. Therefore, as shown in FIG. 37, a delay time (Erase-on delay, De1) for raising the erasing current is provided and the erasing current is raised in a period of the ID gap G2, which is after the E gap passes the ID field and before the E gap reaches a data block start point. A sufficient ID gap G2 length is necessary to absorb a difference in rotation line speeds at an inner track and an outer track on the disk and an error in a leading edge. In this example, the ID gap G2 is determined to have 22 bytes.
When the data block data has been updated, the E gap remains in the data block. Therefore, a delay time to complete erasing is provided and sufficient erasing bands are provided on both sides of the data field. As shown in FIG. 37, the E gap legs behind by the distance d when the update of the R/W gap has been completed. Hence, a delay time (Erase-off delay, De2) for lowering the erasing current is provided to complete erasing on both sides of the data field. The difference in the rotation line speeds at the inner track and the outer track and the difference in the delay time are absorbed in the ID gap G2 and the data block gap G3.
When a data block which is formatted by a FDD with a lower rotation speed is updated by a FDD with a higher rotation speed, data block length (distance in a track) becomes longer and an ID field of a next sector might be damaged. However, when data block gap G3 length is long, a difference in rotation speeds between formatting and writing data in the data block can be absorbed. In a standardized data block gap G3 with a length of 84 bytes for 512 bytes/sector with a length of 84 bytes, an average speed fluctuation (difference) in a sector of .+-.3% can be absorbed. However, the allowable range depends on the distance d which is a function of the structure size of the head. Hence, when the disk becomes smaller, the allowable fluctuation range becomes smaller (refer to FIG. 41 which will be discussed later).
The track gap G4: after the index gap G1 and a nominal number of sectors (each including the sector identifier (ID), the ID gap G2, the data block and the data block gap G3) are written in accordance with an index pulse, the track gap G4 is written until an index pulse after one disk rotation is detected. The gap code "4E" is written in the track gap G4. When the index pulse after one disk rotation is detected, track gap G4 writing is complete and track formatting is complete.
As shown in FIGS. 35 and 36, the number of bytes in the track gap G4 differs according to the disk rotation speed during formatting. Even if the disk rotation speed increases, the last sector is not damaged during formatting as long as the track gap G4 is provided.
For 90 mm 2 HD 2 MB FDC, i.e. high density FDC with a diameter of 90 mm for 2 MB,
A Number of Bytes in a Track excluding a Number of Bytes of the Track Gap G4
=Index gap G1+(Sector Identifier (ID)+ID Gap G2+Data Block+Data Block Gap G3).times.a number of sectors PA0 =146+(22+22+530+101).times.18 PA0 =12296 bytes.
The number of bytes in the track excluding the number of bytes of the track gap G4 is 204 bytes more than a nominal number of bytes, 12500, a nominal rotation number and a nominal bit speed. Hence, 204 bytes is track gap G4 length. As illustrated in FIG. 35, for high speed rotation with approximately 1.6% less cycle time per rotation, the track gap is reduced by approximately 200 bytes (12500 bytes.times.1.6%). However, the track gap G4 of approximately 4 bytes (204 bytes-200 bytes) can still be provided. Consequently, a high speed rotation of approximately 1.6% less rotation cycle can occur during formatting.
As illustrated in FIG. 36, when formatting is performed during a low speed rotation with a low rotation cycle, i.e., a longer cycle time per rotation, recording density becomes higher and the power output during reading decreases. However, a format is not damaged during formatting or during writing and updating.
The index pulse: as stated above, for the flexible disk according to the related art, the index pulse is generated by the sensor provided in the FDD. The index pulse triggers formatting for each track. Formatting of each track is completed by detecting the index pulse after one disk rotation.
Therefore, even if one rotation cycle time of the disk or a write signal frequency fluctuates, the formatting starting and ending positions for one disk rotation do not overlap, thereby ensures that the track is not written over. Further, a space is not generated between the formatting starting and ending positions in one disk rotation. Hence, old data which may cause a malfunction is removed.
The index pulse is detected by the FDD and transmitted to the controlling circuit of the FDD as illustrated in FIG. 33. When the controlling circuit of the FDD is instructed to format by the computer, track formatting is started with the index pulse. When an index pulse after one disk rotation is detected, formatting is stopped and tracks are switched.
For example, for the 90 mm FDC, a highly permeable material is set on a side of the spindle motor at a position in a constant angle with the disk. The index pulse is detected as an electric pulse by a magnetic sensor which does not touch the highly permeable material.
For the 200 mm FDC and 130 mm FDC, a hole on the disk is detected by an optical sensor in the FDD.
Data is read from/written to a formatted disk based on a sector identifier (ID). Therefore, normally, the index pulse is only used for formatting.
The formatting for the 90 mm 4 MB FDC is same as the format of the 90 mm 2 MB FDC except that the 90 mm 4 MB FDC has tracks which each includes 36 sectors, each sector having a recording capacity of 512 bytes. Since the 90 mm 4 MB FDC is a flexible disk covered with a barium ferrite high density magnetic material, a read/write head using a leading erasing method as shown in FIG. 38 is used. Therefore, the length of the ID gap G2 and data block gap G3 and a timing to transmit an erasing current during writing are different from the case shown in FIG. 37. However, in both FDCs, each gap is provided to maintain a connection space during writing or updating.
For a large capacity flexible disk or a hard disk, a track position signal is magnetically written as a servo track during production to ensure high density track position accuracy. In some cases, the servo signal is recorded in a space between sectors on a data recording surface. Generally, when the servo signal is recorded between the sectors on the data recording surface, sectors are formatted based on the servo signal, i.e., the sector servo signal.
However, when the servo signal is recorded on only a surface of a plurality of disks or the servo signal is not recorded magnetically, e.g., optically, the servo signal does not relate to a magnetic data record. In that case, sectors for recording the data are formatted based on the index pulse which is generated according to a mechanical position in a disk rotation. Then, tracks are formatted in a constant pattern using a similar method as that described for the flexible disk.
A sample of a track format for a disk which is illustrated in "The Newest Floppy disk apparatus and its application method" (Shoji Takahashi, 1st edition published on Jun. 10, 1984, pp. 112, 113) is illustrated in FIG. 39. The track format illustrated in FIG. 39 is explained as follows.
Each sector of the track format includes a DID (diskette ID), a LID (Logical ID), data, and gaps (G1-G3) between each two sectors.
The gap G1 corresponds to a preamble and a post-amble in a format according to a related art. The gap G1 is a buffer for a rotation fluctuation during initialization. Since an index signal is not used, the gap G3 in a last sector is written over the gap G1 which is first written. The number of bytes in gap G1 is different for each track. In the DID, a sync. (synchronous signal), an address mark, a diskette ID number, a track number, a block (sector) number, a RL (Record Length) which shows a data length of a data field, and a checking CRC (Cyclic Redundancy Check) are recorded.
In the LID, the same information as for the DID, except a diskette ID number is recorded.
In FIG. 39, the disk does not have an index hole. Therefore, a timing to start track formatting is not controlled.
A procedure for achieving the track format illustrated in FIG. 39 is discussed.
In a first disk rotation, the DID is written in a track. In a second disk rotation, the LID is written in the track. When the LID is written, the DID is referred to. In a third disk rotation, the data is written in the track. When the data is written, the LID is referred to.
Accordingly, the formatting illustrated in FIG. 39 is performed in three disk rotations including writing the data. Formatting without writing data requires at least two disk rotations. Therefore, two or more connections of recording signals exist in a track.
Another track format example is illustrated in FIG. 40.
In FIG. 40, 1st to 16th sectors are formatted in a non-sequential order. The consecutively numbering sectors are separated to provide a waiting time, for example, between the first and second sectors when the first and second sectors are accessed consecutively. If the first and second sectors are placed next to each other, after the first sector is accessed, the second sector must be accessed after one disk rotation. However, due to the skewed layout illustrated in FIG. 40, the second sector can be accessed immediately after the first sector is accessed without waiting for one disk rotation. Hence, data can be accessed from the disk at high speed.
In FIGS. 41 and 42, track formats according to the related art are compared. In FIGS. 43-48, examples of format calculations in the formatting method according to the related art are shown.
In FIG. 41, an unformatted capacity U, a formatted capacity F, etc. of a standardized disk according to the related art are shown. The ratio of formatted capacity F to unformatted capacity U is the format efficiency rate F/U. The format efficiency rate, i.e., a usage efficiency rate, of the track formats according to the related art is 73.5%-73.7%.
The number of bytes in each element on the standardized disk according to the related art is shown in FIG. 42. In FIG. 42, a fluctuation (.alpha.%) of an average speed in a sector from a nominal value and a fluctuation (.beta.%) of one rotation speed are also shown.
A nominal allowable fluctuation value of the average speed in the sector is 2%-3.5%. However, a range of 2.56%-3.98% is allowable. An allowable range of fluctuation in one rotation speed is 1.7%-4% on the high speed side.
Specifically, the number of bytes and allowable fluctuation values differ according to a distance between an erase gap and a R/W gap of the head, an accuracy of a write clock frequency, a leading edge of a write current, a trailing edge of a write current, a leading edge of an erasing current, and a trailing edge of an erasing current. Therefore, examples are shown in FIGS. 41 and 42 and FIGS. 43-48 which are discussed below.
In FIGS. 43-48, formats for standardized disks according to the related art as shown in FIGS. 41 and 42 are calculated as follows. Since calculation methods in FIGS. 43-48 are the same, the calculation method discussed below with reference to FIG. 43 applies also to FIGS. 44-48.
In FIG. 43, a so-called hard index method in which a magnetic head of a tunnel erasing method and an index pulse of an index sensor are used. Values of the distance d between the E gap and the R/W gap, the frequency of the write clock, the nominal clock frequency, a nominal rotation number, a rotation angle speed, an angle recording density, a nominal unformatted bit number in a track (nominal number of bits in a track), a nominal unformatted byte number in a track (nominal number of bytes in a track), an inner track radius, an outer track radius, a nominal bit length at the most inner track, a nominal bit length at the outer track, a bit recording density at the inner track, and a bit recording density at the outer track are shown in FIG. 43. In FIG. 43, a calculation of a number of bytes in each element is shown for each case with an average speed fluctuation (.alpha.) of .+-.0%, .+-.1%, .+-.2%, .+-.3.87%, .+-.4% and .+-.5% in a sector from a nominal value.
Nominal values and calculated values for .alpha.=.+-.3% are discussed as follows.
The index gap G1 has 146 bytes and the sector identifier (ID) has 22 bytes. The ID gap G2 has 22 bytes. The data block has 512 bytes for recording a data and 530 bytes for writing a synchronous code and an error check code. When .alpha.=.+-.3%, the data block gap G3 needs at least 73 bytes.
When the number of bytes of the sector identifier (ID), the ID gap G2, the data block, and the data block gap G3 are accumulated, a number of bytes for a sector is 647 bytes.
According to this standard, there are 15 sectors in a track. Therefore, a track needs a capacity of 647.times.15+146=9851 bytes. Since the nominal number of bytes in a track is 10416 bytes, a difference of 565 bytes from the necessary number of bytes remains as the track gap G4. A value obtained by dividing the track gap G4 length of 565 bytes with the number of bytes in a track of 10416 bytes is an allowable value one rotation speed fluctuation. In this example, a value which is 565 bytes/10416 bytes.times.100=5.4% less is allowable. It is 100/(100-5.4)=+5.7% in a rotation number.
In FIG. 43, values for .alpha.=.+-.3.87% correspond to a format standardized by JIS and ISO. These values are shown in FIG. 42. In FIGS. 43-48, underlined values are maximum values which are applicable for a disk format standardized by JIS and ISO. These values are also shown in FIG. 42. Values of Erase-on Delay De1 and Erase-off Delay are necessary erasing delay time to enter the ID gap G2 (22 bytes).
Recently, a micro-FDD which can be set in a type 2 slot with a thickness of 5 mm of a PC card interface, such as a JEIDA/PCMCIA (Japan Electronic Industry Development Association/Personal Computer Memory Card International Association) card has been developed. A micro-FDC with a disk diameter of approximately 44 mm which can be set in the micro-FDD has been also developed. Both the micro-FDD and the micro-FDC have limited space. Therefore, it is difficult to set a sensor for generating an index pulse as in the FDD and FDC according to the related art.
When it is difficult to set an index sensor in a reduced-sized flexible disk apparatus, formatting may be performed from an arbitrary position in a constant number of bytes without an index pulse as shown in FIG. 39.
When disk rotation speed decreases or write signal frequency increases, formatting is completed before one disk rotation. Even so, a space is not generated and an old sector identifier (ID) is removed according to the case shown in FIG. 39.
However, when disk rotation speed becomes higher, a first sector might be damaged by being written over before a data block gap G3 in a last sector is written. When longer lengths of the ID gap G2 and the data block gap G3 are provided to absorb speed fluctuation caused by a short cycle of a spindle motor, the possibility of damaging a first sector when writing of a last sector increases, which may cause a malfunction.
As stated above, the formatting method shown in FIG. 39 requires at least two disk rotations. Therefore, formatting takes a long time.
Data accessing can be performed at high speed using the format as illustrated in FIG. 40. A skewed sector layout in FIG. 40 improves the efficiency for accessing consecutive track sectors. It is also necessary to improve data accessing speed in different tracks. The format illustrated in FIG. 37, however, cannot improve the data accessing speed in the different tracks.